I am helping 2500HD6.0 put his STS kit on and he just ordered (overnight) a 255 fuel pump. His new tune is showing up to day but that is for his stock fuel pump with 42# injectors.
(He won't run it to hard on the stock pump for fear of going boom)

If we put the new fuel pump in before he gets a tune for it will this hurt anything?

Does he have to retune for the new fuel pump before running it hard? (Think safely it will only take a few days to get a new tune but that’s along time when you have turbo noises following you around.)